首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlik
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlik
admin
2017-08-15
37
问题
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the world’s volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth’s surface; on the contrary, many of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates.
That the plates are moving is not beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth’s interior. It is not possible to determine whether both continents are moving in opposite directions or whether one continent is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layers of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot spot population it appears that the African plate is stationary and that it has not moved during the past 30 million years.
The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate come to rest over a hot spot, the material rising from deeper layer creates a broad dome. As the dome grows, it develops seed fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain their mutability (inconstant).
That Africa and South America were once joined can be deduced from the fact that ______.
选项
A、the two continents are still moving in opposite directions
B、they have been found to share certain geological features
C、the African plates has been stable for 30 million years
D、over 100 hot spots are scattered all around the globe
答案
B
解析
本题可参照文章的第2段。从中可知,因为有新物质深入洋底,所以两个大陆距离愈来愈远;互补的海岸线以及似乎横跨海洋的地质地貌特征提示人们——这两块大陆曾经连接在一起;人们既不能确定是否这两块大陆在向相反的方向移动,也不能确定是否其中的一块大陆静止不动,而另一块大陆正在远它而去;根据热点密度的分析可以看出,非洲板块静止不动了的3000万年。据此可知,人们之所以认为非洲和南美洲曾经连在一起,是因为它们的某些地质特征相似。B项与文章的意思相符,因此B项为正确答案。
转载请注明原文地址:https://jikaoti.com/ti/sUmYFFFM
0
考博英语
相关试题推荐
Over-cultivationandalongperiodoferosionhasreducedthe_____ofmuchofthecountry’sfarmland.
Therelationshipbetweentechnologyanddevelopmentiscomplicated.Attimesthenegativefeaturesoftechnologyseemto_____the
IrecallhowannoyingitwasyearsagowhensmokingeverywherewaslegalinCalifornia.Manycomplainedabouttherestrictionsw
Thenormalhumandailycycleofactivityisofsome7-8hours’sleepalternationwithsome16-17hours’wakefulnessandthatthe
Differentculturesaremoreproneto_____certainillnessesbecauseofthefoodthatischaracteristicinthesecultures.
Readthefollowingpassagecarefullyandthenparaphrasethenumberedandunderlinedparts.("Paraphrase"means"toexplainthe
Thirty-onemillionAmericansareover60yearsofage,andtwenty-ninemillionofthemarehealthy,busy,productivecitizens.By
Themulti-billion-dollarWesternpopmusicindustryisunderfire.ItisbeingblamedbytheUnitedNationsforthedramaticris
Everyoneitseemshasahealthproblem.AfterpouringbillionsintotheNationalHealthService,Britishpeoplemoanaboutdirty
TheAmericandreamismost______duringtheperiodsofproductivityandwealthgeneratedbyAmericancapitalism.
随机试题
速度控制回路有几种方式,其中()调速回路应用于功率较小、负载变化不大的液压系统中。
A.病理性Q波或QS波,ST段抬高,1波倒置B.心电图除aVR导联外,其他导联均呈弓背向下型抬高、T波倒置,无异常Q波出现C.V1、V2、V3导联呈QS型,ST段抬高,T波双向D.病理性Q波已发生半年,ST段仍持续抬高E.Ⅱ、Ⅲ、aVF、V5-V6
下列关于甲状腺功能亢进症的叙述,正确的是
根据《中华人民共和国进出境动植物检疫法》及其实施条例的规定,不论输往国家是否有特殊要求,出境货物的木质包装及动植物性铺垫材料均须依照规定实施检疫。 ( )
关于合规政策的落实,负责执行合规政策,确保发现违规事件时及时采取适当的纠正措施的主体是()。
国别风险与其他风险是并列的关系。()
国有工业企业甲企业为增值税的一般纳税人,2002年6月份发生有关流转税的经济业务如下。(1)购入A材料一批,增值税发票上注明材料价款为30000元,增值税5100元,另支付材料运输费1000元。材料验收入库,款项均已通过银行付讫。(
关于集团项目组向组成部分注册会计师通报的内容,下列说法中,恰当的有()。
8,12,18,27,()。
马克思、恩格斯指出,人类将实现从必然王国向自由王国的飞跃。这里的自由王国指的是
最新回复
(
0
)